A good article from the Guardian
At any moment, one of Britain’s four Trident submarines is out there, somewhere, patrolling a continent-sized patch of the Atlantic. When the 160-strong crew slip beneath the waves off Scotland’s west coast, that’s the last anyone sees of them for three months. Powered by a nuclear reactor, the submarines are almost silent and virtually undetectable. While on patrol, direct communication with navy bosses back home ceases, so potential enemies cannot intercept any signals. The crew are almost completely cut off from the outside world.
Read the rest here